I hit this error when I deployed an app built with Entity Framework onto Windows Azure. Obviously, I wasn’t explicitly using DataReader so it kind of puzzled me. As it happens every time It worked well with local database, application running local and database on SQL Azure. But once I used the Dev Fabric to test the application locally, it failed and gave the above error.

Entity Framework relies on using Multiple Active Results Sets (MARS), and it would be a part of connection string multipleactiveresultsets=True. Earlier SQL Azure didn’t support MARS, so we have to explicitly set it to “false” before deploying to SQL Azure.